Jumble letters - Except the first and last one, to keep it readable

jumble_letters.js

// Jumble letters - Except the first and last one, to keep it readable
const jumbleWord = m => m[0] + [...m.substr(1, m.length - 2)].reverse().sort(() => Math.round(Math.random())).join('') + m[m.length - 1];
const jumbleText = (t, i = 3) => t.replace(/\b\w(\w{2,})\w\b/gi, m => [...Array(i)].map(_ => jumbleWord(m)).find(e => e != m) || m);

// Test
let testText = "It doesn't matter in what order the letters in a word are, the only important\n"
  + "thing is that the first and last letter be at the right place. The rest can\n"
  + "be a total mess and you can still read it without problem. This is because\n"
  + "the human mind does not read every letter by itself, but the word as a whole."

console.log(jumbleText(testText, 5));
console.log(jumbleText('If you can read that, your brain probably working fine.', 10));
// Output
// > It deosn't mettar in waht oderr the leretts in a wrod are, the olny inatrompt
//   tnhig is taht the fsirt and lsat lteter be at the rghit palce. The rset can
//   be a toatl mses and you can slitl raed it wtouhit polebrm. Tihs is bacseue
//   the hmuan mnid deos not raed eevry lteter by iletsf, but the wrod as a wolhe.